1. Field of the Invention
The invention relates to a feed pump for feeding fuel out of a fuel tank of a motor vehicle or for feeding washing fluid of a windshield washing system, the feed pump including a casing, an impeller arranged in the casing and connected on a driven shaft such that the impeller is fixed with respect to rotation relative to the driven shaft and such that a portion of the impeller is arranged with a slight clearance relative to the casing.
2. Description of the Related Art
Feed pumps for feeding fuel out of a fuel tank or for feeding washing fluid for a windshield washing system are typically designed as peripheral pumps or side-channel pumps and are known from practice. Each of these known pumps includes an impeller with guide blades for accelerating a medium to be fed and feeding the medium from an inlet channel to an outlet channel. The guide blades are shaped appropriately for the maximum possible efficiency. Accordingly, it is essential that the impeller be mounted in the intended direction of rotation during assembly in a pump casing. A shaft of the electric motor which drives the impeller usually has a lateral flattening at its free end and the impeller has a recess configured in conformity to the free end of the shaft for receiving the free end of the shaft. However, the dimensions of the guide blades for feeding fuel or washing fluid in a motor vehicle are usually very small and can therefore be ascertained only with great difficulty. As a consequence, there is no guarantee of a faultfree mounting of the impeller.
The object of the present invention is to design a feed pump such that the feed pump can be assembled in a particular simple and faultfree manner.
The object is met according to the present invention by a feed pump having an impeller connected to a shaft driven by an electric motor and at least one of the shaft and the impeller has means for mounting the impeller and shaft in the correct relative position.
This configuration prevents mounting of the feed pump when the impeller is not arranged in its intended position thereby ensuring that the impeller is arranged in its intended position on the shaft when the feed pump is mounted. This configuration prevents the impeller from being arranged out of place on the shaft, so that its direction of rotation in which the feed pump has high efficiency is fixed reliably. As a consequence, the impeller may be mounted in a very simple and faultfree way even when the guide blades have very small dimensions.
According to an embodiment of the invention, the means for mounting the impeller in the correct position are configured particularly simply in terms of design when the means for mounting the impeller in the correct position include a projection arranged near one of the end faces of the impeller arranged for engaging into a step-like recess of the shaft. The recess is configured in conformity to the projection. The shaft is held axially nondisplaceably with respect to the casing. Accordingly, the casing may be mounted only when the impeller is fastened in the correct position on the shaft.
According to another embodiment of the invention, the means for mounting the impeller in the correct position require a particularly low outlay in terms of construction when the means for mounting the impeller in the correct position include two flattenings on the outer surface of shaft which are nonparallel and/or have different dimensions and are arranged for connection to a correspondingly configured recess of the impeller. The connection is positive in the direction of rotation. This configuration allows the correct mounted position of the impeller on the shaft to be ascertained before the casing is mounted.
The feed pump according to the present invention has particularly high efficiency when the impeller includes means for the moveability of an outer edge of the impeller in a pivoting direction relative to the shaft of the electric motor about an axis arranged transversely to the shaft and/or in an axial direction relative to a radially inner region of the impeller. This configuration allows the radially outer region of the impeller to be tilted or slightly displaced by an intended amount in the casing. The position of the impeller in the casing may thereby be adapted in response to forces of an axial bearing acting between the impeller and the casing. The means for movability of the outer edge of the impeller leads to a simple assembly of the feed pump because the invention obviates the need for a particularly accurate mounting of the impeller. Rubbing of the impeller on the casing is reliably avoided as a result. Furthermore, the formation of noise is kept particularly low due to the present invention.
To generate the pivotability of the impeller with respect to the shaft, a particularly large play may be arranged between the impeller and the shaft. However, the large play produces rattling noises when the shaft is driven and in the case of fluctuations in flow in the feed pump. According to an embodiment of the present invention, rattling noises may be kept particularly low when the impeller has, in its region adjacent to the shaft, a depression which surrounds the shaft. This configuration allows the connection of the impeller to the shaft to be restricted to intended dimensions for an intended height of the impeller. In the case of the very small play of the impeller with respect to the shaft, these dimensions are critical for the intended pivotability of the impeller. Another advantage of this configuration is that the impeller does not rub on the casing in the region of the depression.
The depression may be arranged on one end face of the impeller. However, the generation of noise in the feed pump according to the present invention is further reduced when a depression is arranged in each of the two end faces of the impeller.
According to another embodiment of the invention, play between the shaft and the impeller is kept particularly low, along with an intended pivotability of the impeller, when the impeller is designed to be elastic at least in its radially inner region. In the most favorable case, the impeller may be pressed on the shaft. The elastic design of the radially inner region allows simple pivotability and axial movability of the radially outer edge of the impeller.
The elastic region of the impeller could be generated, for example, by the impeller having in this region an insert consisting of an elastic material. However, according to another advantageous development of the invention, the elastic region of the impeller is particularly cost-effective when the impeller has a groove arranged concentrically to the shaft.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.